1. Field of the Invention
The embodiments of the invention generally relate to data storage systems, and, more particularly, to power consumption management for data storage systems.
2. Description of the Related Art
Power consumption is a major issue for large storage systems, and important in general. Currently, users must suffer a loss of performance to achieve significant power savings in a storage array by powering down disks (i.e., placing them in standby). If an input/output (IO) request requires access to a disk that is in standby (i.e., powered down), there may be a substantial delay (e.g., up to or exceeding 10 seconds) before the disk becomes operational. In redundant array of independent disks (RAID) systems (e.g., as illustrated in U.S. patent application Ser. No. 10/619,648 of Hetzler et al., filed on Jul. 14, 2003, and incorporated herein by reference) the redundancy provides an opportunity to at least maintain read access by powering down a fraction of the disks equal to the redundancy. However, in high efficiency arrays, such as RAID 5 or RAID 6, the redundancy is insufficient to provide significant power savings and still guarantee read access, for example, 1 disk out 8 in a 7+P RAID 5. Additionally, since writes still require the disk to be active (i.e., powered up), this rate of power savings can be easily lost during the power-up process if disks are placed in standby too often.